I think it depends. If we're talking about certain mediums that require complex code then I really don't know if a designer can gain a lot from that experience

I think it depends. If we're talking about certain mediums that require complex code then I really don't know if a designer can gain a lot from that experience over simply talking with an experienced developer to gain a high level understanding of what's possible. I'm mostly a designer and I did Paul Hegarty's Developing iOS 9 Apps with Swift course out of curiosity. I've also done courses on Ruby and Python. And I worked on Rails and Coffeescript for a number of years. While I appreciate the experiences, I don't consider myself a better designer from it over say, those who spent that time getting stronger at illustration or user testing or color theory. The person who spends 40 hours a week doing Swift/Ruby/Python is clearly going to be much more proficient than some asshat like myself who dabbles in it once in a while. Sure, it's helpful in a situation where you and a friend want to experiment with testing a startup idea and you divide the roles, but for most situations the clear division of labor is much more efficient. However, I don't think there's any reason why designers, specifically those who produce work for the web, shouldn't learn basic HTML/CSS or if a bit more ambitious, React and Javascript. All those languages are fairly approachable and can help with prototyping and experimentation.